I am in the process of restoring an old RCA mantle radio from the mid 30s, a T4-10. I have replaced all
the caps and resistors yet the raio still performs
quite badly. The output is soft and distorted even with the pot turned all the way up. Is this typical of
the TRF sets coming out in the early to mid 30s? Most of my experience has been with the super hets coming out in the later 30s and 40s which all seem to
work better. As a side note, one of the tubes seems to
be displaying a blue glow inside of it. I was told -
many years ago - that this may be due to a "gas" problem, indicating that the tube may be bad. Right or
wrong? Let me know. Thanks

:I am in the process of restoring an old RCA mantle radio from the mid 30s, a T4-10. I have replaced all
:the caps and resistors yet the raio still performs
:quite badly. The output is soft and distorted even with the pot turned all the way up. Is this typical of
:the TRF sets coming out in the early to mid 30s? Most of my experience has been with the super hets coming out in the later 30s and 40s which all seem to
:work better. As a side note, one of the tubes seems to
:be displaying a blue glow inside of it. I was told -
:many years ago - that this may be due to a "gas" problem, indicating that the tube may be bad. Right or
:wrong? Let me know. Thanks

::I am in the process of restoring an old RCA mantle radio from the mid 30s, a T4-10. I have replaced all
::the caps and resistors yet the raio still performs
::quite badly. The output is soft and distorted even with the pot turned all the way up. Is this typical of
::the TRF sets coming out in the early to mid 30s? Most of my experience has been with the super hets coming out in the later 30s and 40s which all seem to
::work better. As a side note, one of the tubes seems to
::be displaying a blue glow inside of it. I was told -
::many years ago - that this may be due to a "gas" problem, indicating that the tube may be bad. Right or
::wrong? Let me know. Thanks
:

:Tubes that glow blue usually are the result of the tube going gassy - meaning that there is a leak in the envelope or some other contamination. The tube should be replaced - it is probably the source of your distortion.

When I restored an early 1930s TRF set one of the type 24As in the RF front end was glowing blue. The output of the radio was horribly distorted. A new tube cured the problem.

PS: TRF sets usually should have great fidelity - no mixing stage causing distortion results in a cleaner output.

Lou

::I am in the process of restoring an old RCA mantle radio from the mid 30s, a T4-10. I have replaced all
:::the caps and resistors yet the raio still performs
:::quite badly. The output is soft and distorted even with the pot turned all the way up. Is this typical of
:::the TRF sets coming out in the early to mid 30s? Most of my experience has been with the super hets coming out in the later 30s and 40s which all seem to
:::work better. As a side note, one of the tubes seems to
:::be displaying a blue glow inside of it. I was told -
:::many years ago - that this may be due to a "gas" problem, indicating that the tube may be bad. Right or
:::wrong? Let me know. Thanks
::
:
:

Early TRF sets with moving-iron loudspeakers typically sound "tinny" to most people because they had poor low-frequency response when brand new. Some later TRF sets used paper-cone dynamic speakers ("Kellogg-Rice" speakers) and were capable of a much wider range of sound reproduction- when the set is working correctly, these old sets can still sound excellent. However, they are still prone to various electrical faults that will degrade sound quality: (1) low B+ voltage from a failing rectifier tube; (2) incorrect grid bias on the audio amp stage tubes due to resistor drift; (3) bad tube; and (4) mechanical problem with speaker (voice coil rubbing in the field channel, "petrified" cone material, etc).

A glowing tube generally is a bad tube, since any gas inside the tube will ionize and delinearize the tube's response even more than it already is.

::I am in the process of restoring an old RCA mantle radio from the mid 30s, a T4-10. I have replaced all
::the caps and resistors yet the raio still performs
::quite badly. The output is soft and distorted even with the pot turned all the way up. Is this typical of
::the TRF sets coming out in the early to mid 30s? Most of my experience has been with the super hets coming out in the later 30s and 40s which all seem to
::work better. As a side note, one of the tubes seems to
::be displaying a blue glow inside of it. I was told -
::many years ago - that this may be due to a "gas" problem, indicating that the tube may be bad. Right or
::wrong? Let me know. Thanks
:
Hi, is your resistor line in the AC cord good? looks like it should be around 315 ohms. The glow could be a gas short do you have a tester or another tube to try? Best 2 U, George T